[Table of Contents]

Plasma and Fusion Research

Volume 10, 1402083 (2015)

Regular Articles


Morphology and Optical Property Changes of Nanostructured Tungsten in LHD
Shin KAJITA, Tsuyoshi AKIYAMA1), Naoaki YOSHIDA2), Masayuki TOKITANI1), Miyuki YAJIMA1) and Noriyasu OHNO3)
EcoTopia Science Institute, Nagoya University, Nagoya 464-8603, Japan
1)
National Institute for Fusion Science, Toki 509-5292, Japan
2)
Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
3)
Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan
(Received 21 May 2015 / Accepted 16 September 2015 / Published 28 December 2015)

Abstract

Nanostructured tungsten formed by the exposure to helium plasma in a linear plasma device was installed in the large helical device (LHD). After the exposure in a series of experiments in the 2012 fiscal year campaign in LHD, the samples were analyzed by scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersion x-ray spectroscopy (EDX). It was found that part of the nanostructures was totally covered with carbon based material probably from divertor, while some other parts were eroded by sputtering. On the erosion dominant region, it was revealed that the head part of nanostructures was sputtered and the surface became rounded, but the nanostructures still remained near the surface. Optical reflectance of the material was measured, and it was found that the morphology changes increased the optical reflectivity up to ∼10% from typically less than 1%. The possibility and limitation of the nanostructured tungsten as a light absorber (viewing dump) are discussed.


Keywords

nanostructured tungsten, large helical device (LHD), deposition, sputtering

DOI: 10.1585/pfr.10.1402083


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This paper may be cited as follows:

Shin KAJITA, Tsuyoshi AKIYAMA, Naoaki YOSHIDA, Masayuki TOKITANI, Miyuki YAJIMA and Noriyasu OHNO, Plasma Fusion Res. 10, 1402083 (2015).